JPH02275835A - Method for recovering citric acid from solution containing citric acid - Google Patents

Abstract

Process for the recovery of citric acid from a liquor containing it, characterised in that, successively, - in a first stage the liquor containing citric acid is brought into contact with an R cationic resin in hydrogen form for a sufficient time to reach an optimum adsorption of citric acid, - in a second stage the resin is treated with an eluting agent and the eluate fraction which is rich in purified citric acid is recovered. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for recovering citric acid from a citric acid-containing liquid.

The expression "liquid" here refers to fermentation liquid and citric acid yeast liquid.

[Prior Art] It is known to produce citric acid by crystallization from sufficiently concentrated and enriched syrups. It is also known to produce syrup from fermentation liquor. Regarding these, normally, the fermented liquor from which mycelia have been removed is treated with lime, and then soluble impurities are removed, and the produced insoluble calcium citrate is recovered by filtration. This calcium citrate is decomposed with sulfuric acid to liberate citric acid. Calcium sulfate produced in this reaction is decomposed by filtration, and residual cations are removed by passing the citric acid-containing filtrate through an ion exchange resin operated in a hydrogen cycle under conditions that adsorb only cations.

The above method, which allows the removal of minerals as well as organic soluble impurities present in the fermentation liquor and provides a solution with a sufficiently high citric acid content for the precipitation of citric acid in good yields, however, It has the major drawback of being consumed in large quantities and producing large amounts of calcium sulfate, which is an environmental pollutant and cannot be recycled or reused.

In order to overcome these drawbacks, many people skilled in the art have tried to provide other methods by which the impurities contained in the citric acid fermentation liquor can be partially removed. Many of these methods are based on extracting the citric acid contained in the liquid with an organic solvent.

For various reasons, these methods were not completely satisfactory and did not reach industrial development.

Other purification methods employed to separate the majority of impurities consisting of high molecular weight particles are - reverse osmosis filtration membranes or ultrafiltration to remove the high molecular weight molecules mentioned above, - or non-filtration to adsorb the above mentioned impurities. Ionic adsorbent resins are based on the use of either.

However, this adsorbent resin must be regenerated with alkali and organic solvents after each adsorption cycle.

Furthermore, in both cases, the low molecular weight ionic impurities that were not separated from the citric acid, in particular the ionic impurities consisting of mineral cations and anions, were removed from the anionic resin as far as the cationic resin was concerned. As far as it is concerned, it is removed by flowing the liquid through a cationic and anionic resin under the condition that only the anions of the strong mineral acid are adsorbed, and purification is carried out by ion exchange. Once the resin is saturated, cations are eluted with a strong acid solution, typically hydrochloric acid, and single ions are eluted with a strong base solution, typically caustic soda, to elute the adsorbed impurities. In this way, the resin is recycled,
Ion exchange purification cycles are followed, and these methods have therefore not been developed on an industrial scale because they are very costly and difficult to operate.

[Problem to be Solved by the Invention] Since none of the known methods is satisfactory, the applicant proposes to recover citric acid from a citric acid-containing fermentation solution or crystallization mother liquor using sulfuric acid or an organic solvent. Efforts have been made to find an easier and more economical way to do this without having to do so.

[Means for Solving the Problems] The method of the present invention that achieves the above effects has the following features. That is, in the first step, the citric acid-containing liquid is brought into contact with the hydrogen type cation resin for a sufficient period of time to achieve maximum adsorption of citric acid, and in the second step
The process treats the resin with an eluent and collects a purified citric acid-rich eluate fraction.

It consists of a continuous process called.

The raw material used for citric acid fermentation usually consists of sugar honey, but pure carbohydrates can also be used.

In the latter case, this citric acid fermentation can ensure that a liquid very low in impurities is obtained, which allows at least the first crystallization of citric acid without purification.

Only the crystal mother liquor is then treated with the second or third method for extracting crystallized citric acid according to the invention.

Preferably, the liquid that comes into contact with the resin is warm, and the temperature is advantageously 50-95°C, more preferably 65°C.
-80°C.

According to an advantageous embodiment of the invention, the eluent consists of water, the temperature of which is higher than 40°C, preferably 50°C.
-95°C, more preferably close to the temperature of the liquid to be treated.

According to another advantageous embodiment according to the invention, the filling resin has a small particle size and a low rate of reticulation with divinylbenzene, preferably a cationic resin of the styrene-divinylbenzene type.

The reticulation percentage of the resin is usually between 5-10%, preferably between 4-8%, and the particle size of the resin is 0.5%.
It is between 1-1 mm, more preferably between 0.2-0.6 mm.

In order to achieve maximum adsorption of citric acid, i.e. adsorption of at least about 90% of the total amount of citric acid contained in the liquid, a given fraction of the liquid must be in contact with the resin for 20 minutes to 10 hours. Must be in contact, 1-31/2
Preferred is a contact time of 0.1-3 volumes per resin volume per hour, preferably 0.1 to 3 volumes per resin volume per hour.
This corresponds to a discharge of 3-1 volumes. .

The invention also contemplates other features disclosed below, which in any case will be better understood by the following description and non-limiting examples of advantageous embodiments. The description and examples are illustrated by the drawings. The fermentation liquor or crystal mother liquor, in which the solids content is generally 10 to 75% by weight, particularly close to 50% by weight, and in which most of the citric acid is in the free form, is first treated with a hydrogen-type cation exchange resin and the cations of the raw material. contact under conditions such that all of the protons are exchanged for protons. Although this pretreatment is not necessary, it will prevent the formation of a shell of deposits on the evaporator and thus extend the life of the adsorption resin.

Next, the liquid to be purified is brought into contact with a selected resin.The selected resin is, for example, selected from the group consisting of the following resins. These trademarks are as follows.

-TSW40 Sold by BAYER -C204
Sold by DUOLITE - DIAION 5KIBS Sold by Mitsubishi - CFX4 5YBRON') In this case,
The resin is preferably packed in a column with a thermostatted jacket. A column jacket is not necessary if the Simension equipment is such that heat loss is not a major drawback.

Selection of contact time is one requirement to maximize citric acid adsorption.

Next, the resin is eluted. In this case, preferably hot water can be used, the temperature of which is close to that of the raw material, generally 5
The temperature is 0 to 95°C.

In practice, the elution rate is 0.1 to 3 volumes, preferably 0.3 to 1 volume of eluent per resin volume and time.

The eluted fractions were partially collected and divided according to the results of analysis.

Unexpectedly and surprisingly, the first eluted fraction essentially contains, besides cations, high molecular weight products and unfermented sugars, i.e. saccharose, maltose, isomaltose, etc. The fraction contains extremely pure citric acid, and the last two fractions contain gluconic acid, oxalic acid, and various other organic acids, as well as compounds that are strongly adsorbed to the resin, such as bedine, and culture. compounds obtained from the components of the medium,
It was found that it contained compounds synthesized during fermentation along with citric acid.

The fraction containing citric acid is concentrated to a concentration sufficient to crystallize citric acid, that is, about 60% by weight or more, and the crystallized citric acid is then separated by filtration.

According to the method of the present invention, citric acid can be almost completely separated from impurities contained in the liquid, and the result is obtained without consuming chemical products or producing by-products that reduce purity. .

To carry out the method according to the invention, it is possible to use one to several chromatographic columns, operating in series or in parallel and continuously or discontinuously. These columns must be equipped with suitable means for feeding feed material and eluent to the columns. Furthermore, suitable means must be provided for collecting successive fractions of the eluate.

To illustrate, FIG. 1 is an example of a single column, discontinuously operated apparatus. A device running several columns in series can undoubtedly give better results. Particularly preferred is a device of the type disclosed in French Patent Specification No. 7910564, in which the results are equally dependent on the dry matter content of the various components, including purified citric acid on the one hand and impurities on the other hand. It is expressed as the dry weight of purified liquor per hour per volume of resin. It must be made clear that the contents of the various fractions separated are the same no matter which device is used.

The single column device shown in FIG. 1 consists of a glass column 1 with a jacket 2, the capacity of which is 3.
50m1. It has a diameter of 1.5 cm and a height of 2 m. The column is made of strong ionic resin designated R, such as the trademark “C2O4
The column is packed with 339 ml of divinylbenzene 8% cross-linked resin sold by DUOLITE.The column jacket is supplied with water whose temperature is automatically controlled by vibrator 3, and is discharged by vibrator 4 to maintain the temperature of the resin. Make sure to keep it at 75℃.

The resin is percolated with a 1.2N aqueous hydrochloric acid solution at 10100O to its acid, ie hydrogen, form.

To carry out this percolation, hydrochloric acid is brought to the top of the column, vibrate 5, by means of a vibro. Water for washing is subsequently conveyed through the same piping. Percolation and washing are performed at a rate of about 2 volumes of liquid per volume of resin per hour. Water 20001 for washing
is used. The liquid is leached from the column by the vibrator 7.

Vibrator 7 is differentiated by Vibrator 8 Fractometer 9
join to. This meter is capable of measuring the refractive index of the leachate from the column and thus allows detection of the presence and amount of soluble substances in the leachate. This meter itself is then coupled to a UV detector, indicated at 11, by a line IO. The UV detector operates at 280 nm to detect nitrogen-containing substances. Refractometer-9
and the detector 11 are connected in series.

The detector 11 is connected to a four-way cock 13 by a pipe 12. This four-way cock is suitable for sending the eluate sent through the piping 12 to the fractionation containers 15a, +5b, and 15c, respectively, using the vibrators 14a, 14b, and 14c.

After conversion of the resin in the column to the acid form, an amount of fermentation liquor is injected into the top of the column, and then the liquor is eluted with hot water.

According to the instructions given by the U-detector It and the fractometer 9, the eluate is divided at the outlet of the column into three fractions, each containing - rejected impurities, purified citric acid, and adsorbed impurities. These three portions are introduced into containers 15a, 15b, and 15c, respectively.

[Example] Example! Recovery of citric acid from the fermentation liquid obtained by fermentation in a medium containing starch hydrolyzate as a main component The liquid to be processed contains 89.3% by weight of citric acid based on the dry matter, and is rich in organic and Mineral impurities, 1.1% gluconic acid, 0.5
% oxalic acid, 2% maltose and 2% sulfated ash. The liquid was filtered and the dry matter content was 50
% concentrated. Its density is 1.22 g/ml.

1 ml of the liquid is introduced at the top of the resin column detailed above and shown in FIG.

Elution is carried out using hot water at a rate of 152 ml/hr. The jacketing temperature is approximately 75°C.

The eluate begins to appear at the outlet of the interstitial column at approximately 420°C.The variation of its dry matter volume with respect to the flx (expressed in ml) of the eluate collected is shown in the graph of Figure 2 as a function of the refractive index ( This is embodied by a curve C1 represented by the amount of change yl (arbitrary scale) of the refractometer 9).

The curve C1 corresponds to the letter A1. A2. It has three beaks designated A3.

Beak A1 corresponds to the first fraction containing the excluded impurities, and its first fraction of eluate, representing a volume of 16 ml, is led to pipe +4a by means of cock 13 and collected in a glass container 15a.

Beak A2 corresponds to the second fraction containing purified citric acid and has a volume of 43 ml. The fraction is led to pipe 14b by operating cock 13 and collected in glass container 15b.

Beak A3 corresponds to the third fraction containing impurities that are more strongly adsorbed than citric acid, and has a capacity of 36 ml.The fraction is transferred to pipe 1 by newly operating cock 13.
4c and collected in a glass container 15c.

In addition, the amount of change y2 (arbitrary scale) in the optical density of the eluate at 280 nm as a function of the amount of eluate collected as a function of the amount It is embodied by C2.

Curve C2 is practically flat during the duration of the elution, in which case it does not give any factor that allows evaluation of the effect of purification, it is the raw material (starch hydrolyzate) from which the fermentation liquor is made.
This is due to the fact that it is very pure and does not contain substances that absorb ultraviolet light.

Beak A in Table 1! The total amount of dry matter and the ratio of citric acid in the three fractions corresponding to , A2 and A3 are shown below.

From the values listed in Table 1, it can be seen that fraction B, which corresponds to beak A2, accounts for 97% of the citric acid present in the purified liquid.
and its concentration in citric acid is 99%.

Example 2 Recovery of citric acid from a fermentation liquor obtained by fermentation of a medium containing sugar honey as a main component The liquor to be treated contains 63.5% by weight of citric acid based on the dry matter. Organic and mineral impurities such as % gluconic acid, 0.3% oxalic acid, 1.2% fructose, 3.5% glucose, 6.6% disaccharose and 13.5% sulfuric acid. Contains. This liquor was filtered to a dry matter content of 16.5%. Its density is 1.07 g/ml.

2 ml of said liquid is introduced at the top of the resin column already detailed and shown in FIG.

Elution is carried out using hot water at a rate of 162 ml/hr. The jacketing temperature was maintained at 75°C.

The eluate begins to appear at the outlet of the interstitial column at approximately 42°C.The change in its dry matter volume with respect to the volume of eluate collected x (expressed in ml) is expressed as a function of the refractive index as a function of X in the graph of Figure 3. (refractometer 9) by the curve C3 represented by the change yl (arbitrary scale).

Curve C3 corresponds to letters B, , B2 . B3. 4 represented by B.
It has two peaks.

Peak B1 corresponds to the first fraction containing the excluded impurities and exhibiting a volume of 22 ml, that first fraction of the eluate is led to the vibrator 14a using the stopcock 13 and collected in the container +5a.

Peak B2 corresponds to the second fraction containing purified citric acid and has a volume of 59 ml. The fraction is guided to the vibrator 14b by operating the cock 13, and is guided to the container 1.
It is collected in 5b.

Peaks B3 and B4 correspond to the third fraction containing impurities that are more strongly adsorbed than citric acid, with a volume of 54 ml.
By operating the cock 13 again, the fraction shown is guided to the vibrator 14c and collected in the container 15c.

Curve C4 in the graph of FIG. 3 also shows the change in optical density y2 (arbitrary scale) of the eluate at 280 nm, as measured by the detector 11, as a function of the amount X of eluate collected.

Curve C4 beam, ,D2. It has three peaks D3, which represent impurities contained in sugar honey. The impurities represented by peaks D, D3 are again found in fraction B1 as a whole and similar to this impurity 83
+84 is represented by peak D2.

From the above, it has become clear that, according to the method of the present invention, highly pure citric acid can be obtained in high yield even from a liquid with a relatively low concentration of citric acid.

Table If shows the total amount of dry matter and the ratio of citric acid in the above three fractions.

Table n shows that the fraction corresponding to peak B2 contains 94% of the citric acid present in the liquid subjected to the purification treatment, and the concentration of citric acid in this fraction is 98%.

[Effects of the Invention] From the above, it has become clear that the method for recovering citric acid from fermentation liquid of the present invention described in detail so far has the following numerous features compared to conventional methods. .

- Highly purified polycitric acid can be recovered from a citric acid fermentation solution or from a mother liquor from which citric acid has first been separated to some extent by crystallization, by single-stage chromatography treatment.

-Does not consume chemicals.

・Does not generate environmental pollutants.

・Materials known to be stable and harmless (resins)
use.

- Can be incorporated into equipment that has already been subjected to uses other than the method of the invention and is robust and of known performance.

[Brief explanation of drawings]

1 is a schematic diagram of an apparatus for carrying out the method according to the invention; FIGS. 2 and 3 are diagrams showing curves representing the development of the method;
It is.

Claims (1)

[Claims] 1. In the first step, the citric acid-containing solution is brought into contact with the hydrogen-type cation resin for a sufficient period of time to achieve maximum adsorption of citric acid, and in the second step, this is achieved using an eluent. A method for recovering citric acid from a citric acid-containing liquid comprising a continuous process of treating a resin and recovering a purified citric acid-rich eluate fraction. 2. The method of claim 1, wherein the eluent is water. 3. The temperature of the eluent is 40℃ or higher, preferably 50-95℃
2. The method of claim 1, comprising water having a temperature of . 4. The method according to claim 1, wherein the temperature of the liquid in contact with the resin is 50-95°C, preferably 65-80°C, and the temperature of the eluent is close to the temperature of the liquid. 5. The resin used is styrene, which has a small particle size and a low reticulation rate with divinylbenzene.
Cationic resins of the divinylbenzene type are preferred, with a reticulation proportion in the range 5-10%, preferably 4-8%, and a particle size of 0.1-1 mm, preferably 0.2-1 mm.
A method according to claim 1, in the range of 0.6 mm. 6. A predetermined fraction of said liquid is added to the resin for 20 minutes to 10 hours, preferably 1 to 32 hours, corresponding to a discharge rate of 0.1 to 3 preferably 0.3 to 1 volume/volume of resin/hour. 2. The method of claim 1, wherein the method is maintained in contact with. 7. The method according to claim 1, wherein said liquid is obtained from molasses or carbohydrate.